Stabilization of furfural



Patented Aug. 19, 1947 STABlLI ZATION OF FURFURAL Rock L. Comstock,Weeks, La., and Howard F. Reeves, Jr., Wyandotte, Mich., assignors toBay Chemical Company, Inc., NewOrleans, La., a

corporation of Louisiana No Drawing. Original application May 31 1940,Serial No. 338,274. Divided and this application July 6, 1944', SerialN0. 543,736

8 Claims. (Cl. 260-347) This invention relates to the stabilization offurfural.

Furfural is an organic liquid which is normally clear or colorless. Ithas many uses in modern technology, among which are its employment as asolvent or distributing agent and also as a base for certain syntheticresins. Furfural readily condenses with various reagents into largermolecular aggregates to form resinous plastics. However, furfural isnormally unstable so that its tendency to resinify persists to anundesirable degree in the absence of the employment of stabilizingagents. Furfural become altered spontaneously even in storage, toproduce gummy derivatives. These derivatives are dark in color anddarken the furfural in which they are formed, even when present inconsiderable dilution. The dark color of furfural is, therefore,evidence of deterioration of the furfural.

It has heretofore been difiicult to prevent this chemical alteration offurfural to form dark gummy products because the nature of this changeis not known with certainty. It has been supposed to be due tooxidation. It is known that furfural is an organic compound of aheterocyclic system, and that its structure is that of an aromatic-like,five membered ring containing an oxygen atom in the ring, in which thecarbon atoms attached to the oxygen are attached to other carbon atomsby double bond, so that furfural in structure is an unsaturated ring.The accepted chemical structure of furfural is:

An object of this invention is to stabilize furfural against alterationduring storage. A further purpose is to maintain the clarity orcolorless nature of furfural even in the presence of air.

A particular object is to prevent spontaneous formation of dark gummyderivatives in furfural through inhibition of the normal tendency offurfural to polymerize.

This invention accomplishes stabilization of furfural by incorporationtherein of a small proportion of a hydrosulfite, A sufficient amount isused to substantially prevent polymerization. The hydrosulfites of thealkali metals are particularly effective, and of these, the preferredmaterial is sodium hydrosulfite (Na2S2O4). The amount of stabilizerwhich is necessary to effect the desired result is relatively small--thefunction of the inhibitor probably is that of a catalyst rather than asan active reagent. A range of 2 about 0.01% to 1.0% is effective toinhibit undesirable chemical deterioration of furfural, but ordinarily,a range of 0.01% to 0.1% is sufficient, and this latter range ispreferred. In order to determine the eificacy of the alkali metalsulfite inhibitor in accordance with this invention, sodium hydrosulfitein the form of a aqueous solution was added to various samples offurfural in test tubes, the test tubes closed, and then inspected afterstanding for nine months. Similar samples of the furfural were preparedcontaining no inhibitor. In those cases where no inhibitor was used, thefurfural turned black and thickened materially, in some cases becomingalmost solid. When an amount of sodium hydrosulfite solution wasemployed such that the sodium hydrosulfite amounted to 0.1% by weight,the furiural at the end of the test period was a light amber in colorand remained in the form of a thin liquid, Similar results were obtainedwhen 0.02% and 0.01% sodium hydrosulfite were employed. In the lattercases, however, the color of the furfural Was slightly darker, the colorranging from a reddish amber in the case where 0.02% was used to a darkred amber when 0.01% was used. In both cases, the furfural remained inthe form of a thin liquid. No solid deposits were observed in any case.From these results, it is apparent that sodium hydrosulfite possessesexcellent properties for inhibiting the deterioration of furfural.

This application is a division of application, Serial Number 338,274.,filed May 31, 1940.

While in accordance with the patent statutes, the principles of thisinvention have been set forth, and a preferred form thereof has beenillustrated by specific examples, it will be apparent to those skilledin the art that modifications may be employed within the scope of theinvention as defined in the following claims.

We claim:

1. A process of inhibiting the deterioration of normally unstablefurfural comprising incorporating in the furfural a small proportion ofhydrosulfite sufllcient to substantially inhibit deterioration.

2. A process in accordance with claim 1 in which the hydrosulfite is analkali metal hydrosulfite.

3. A process in accordance with claim 1 in which the hydrosulfite is analkali metal hydrosulfite and is in amounts of approximately 0.01% to1.0%.

4. A process of inhibiting the deterioration of normally unstablefurfural comprising incorpo 3 rating in the furfural approximately 0.01%to 1 of sodium hydrosulfite.

5. A stabilized furfural comprising normally unstable furfuralcontaining a small proportion of hydrosulfite, suflficient tosubstantially inhibit deterioration of the furfural.

6. A composition in accordance with claim 5 in which the hydrosulfite isan alkali metal hydrosulfite.

7. A composition in accordance with claim 5 in which the hydrosulfite issodium hydrosulfite.

8. A stabilized furfural comprising normally unstable furfuralcontaining approximately 0.0 to 1.0% of sodium hydrosulfite.

ROCK L. COMSTOCK. HOWARD F. REEVES, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,950,438 Carothers et a1 Mar.13, 1934 2,078,241 Fuhner Apr. 27, 1937 10 2,080,142 Lowry May 11, 1937FOREIGN PATENTS 7 Number Country Date 181,365 Great Britain 1923

